The present invention relates to the field of turbomachines, and more particularly it relates to the interface between the high pressure turbine and the combustion chamber in turbojets having a combustion chamber that is made of ceramic matrix composite (CMC) material.
Conventionally, in a turbomachine, the high pressure turbine (HPT) and in particular its inlet nozzle, the combustion chamber, and also the casing (or xe2x80x9cshellxe2x80x9d) for said chamber are all made of metal type materials. However, under certain particular conditions of use involving very high combustion temperatures, the use of a metal combustion chamber turns out to be completely unsuitable from a thermal point of view and it is necessary to make use of a combustion chamber based on high temperature composite materials of the CMC type. However the difficulties involved in working such materials and their raw material costs mean that their use is usually restricted to the combustion chamber itself, with the high pressure turbine inlet nozzle and the casing continuing to be made more conventionally out of metal materials. Unfortunately, metal materials and composite materials have coefficients of thermal expansion that are very different. As a result, aerodynamic problems that are particularly severe arise at the interface with the nozzle at the inlet to the high temperature turbine, and in the connection between the casing and the chamber.
The present invention mitigates those drawbacks by proposing a casing-to-chamber connection having the ability to absorb the displacements induced by the differences between the expansion coefficients of those parts. Another object of the invention is to propose a structure that is simple in shape and that is particularly easy to manufacture.
These objects are achieved by a turbomachine comprising a shell of metal material containing, in a gas flow direction F: a fuel injection assembly; a composite material combustion chamber; and a sectorized nozzle of metal material forming the inlet stage with fixed blades of a high pressure turbine, wherein said combustion chamber is held in position by a sectorized flexible sleeve of metal material having a first end fixed by first fixing means to said combustion chamber and having a flange-forming second end fixed to said shell by second fixing means. Said first fixing means also serve to connect said combustion chamber to said sectorized nozzle.
By means of this direct attachment (integration) of the combustion chamber to the nozzle, any misalignment of the stream of gas in operation is avoided (thus guaranteeing better feed to the high pressure turbine), while also improving sealing between the combustion chamber and the nozzle. The connection to the shell via a system of sectorized flexible sleeves also provides an appreciable saving in weight for the combustion chamber compared with traditional connection devices having heavy rigid flanges.
The first fixing means are preferably constituted by a plurality of bolts. The flexible sectorized metal sleeve has ventilation orifices to allow a cooling fluid to pass through and a plurality of parallel sectorization slots terminating at the upstream ends of said ventilation orifices. The sectorization slots are dimensioned to compensate for the relative thermal expansion that exists between the combustion chamber made of composite material and the shell made of metal material.
In a preferred embodiment in which the turbomachine comprises a shell having outer and inner annular walls of metal material defining between them a space for receiving in succession, in the gas flow direction F: a fuel injection assembly, and both an annular combustion chamber of composite material formed by an outer axially-extending side wall, an inner axially-extending side wall, and a transversely-extending end wall, and also by a sectorized annular nozzle of metal material formed by a plurality of fixed blades mounted between an outer sectorized circular platform and an inner sectorized circular platform, provision is made for the downstream ends of said outer and inner side walls of the combustion chamber to be held in position by outer and inner flexible sleeves of metal material having first ends fixed to said outer and inner downstream ends by first fixing means, and having flange-forming second ends fixed to said outer and inner annular shells by second fixing means.
Advantageously, these first fixing means comprise both first holding means for holding said downstream end portion of the inner side wall of the combustion chamber between said inner sectorized circular platform of the nozzle and said first end of the inner sectorized flexible sleeve, and also second holding means for holding said downstream end portion of the outer side wall of the combustion chamber between said outer sectorized circular platform of the nozzle and said first end of the outer sectorized flexible sleeve.
Preferably, said first end of the inner sectorized flexible sleeve has a flange-forming downstream portion that serves as a bearing surface for a gasket of the inner annular wall of the shell.
In order to provide sealing in the turbomachine, said inner annular wall of the shell has a flange including a circular groove suitable for receiving a circular gasket of the omega type for providing sealing between said flange and the inner annular wall of the shell and said flange-forming downstream portion.